Development of a Tier-1 Assay for Assessing the Toxicity of Insecticidal Substances Against Coleomegilla maculata

To assess the potential dietary effects of insecticidal substances on the predacious ladybird beetle, Coleomegilla maculata De Geer, a Tier-1 laboratory testing system was developed. Artificial diets using shrimp eggs were developed, and a tier-1 bioassay examining C. maculata development and survival was designed based on those diets. To further measure the artificial diet in a Tier-1 testing system, larvae of C. maculata were fed the diet treated with different concentrations of an inorganic stomach poison, potassium arsenate (PA), or a cysteine protease inhibitor, E-64. The results demonstrated that the testing system was capable of detecting the dietary effects of both substances on the survival and development of C. maculata. With increasing concentrations of PA in the diet, fewer larvae developed to adults, with only 22.7% larvae surviving to the adult stage in the treatment with the highest content of PA (32 mu g/g of diet). Likewise, dose-dependent responses also were found for other life-table parameters of C. maculata. Similar to the assays with PA, the survival rates of C. maculata consistently decreased with increasing E-64 content in the diet. Survival analysis showed that the insects fed E-64 at 50, 150, and 450 mu g/g in the diet had significantly lower survival rates compared with those on the untreated artificial diet. The study presented here describes a robust testing system that will be useful for assessing the potential hazard (or toxicity) effects after dietary exposure of insecticidal compounds produced by GE plants or conventional insecticides on the ladybird predator, C. maculata.